With respect to electrochemical devices such as secondary batteries and electric double layer capacitors, vigorous efforts have been made for achieving various improvements such as reduction in size and weight, increase in capacity and extension of life. In order to keep a positive electrode and a negative electrode of these electrochemical devices to be separated from each other so as to prevent electrical short circuit, a separator made of an insulating material has been used conventionally.
Patent Document 1 discloses an electrochemical cell having an inactive layer serving as a porous separator on an electrode active material. Patent Document 2 discloses a technique concerning a separator which is a porous film formed of a resin material composed mainly of a synthetic resin and filler particles, and having communicating pores.